Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the annotations, the description discloses a critical side effect: 'Adding any image re-triggers AI moderation — the listing returns to pending until the new images are cleared; removing images does not.' It also reveals cost behavior ('Free (no credit)') and enforces the 6-image cap. This is strong behavioral transparency for a mutating tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and well-organized: it front-loads the core action, then provides the required workflow, then states side effects and cost. Every sentence contributes necessary information without redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a photo-update tool with an output schema present, the description covers ownership restriction, prerequisites, moderation side effects, and cost. No critical behavioral detail needed to call the tool safely is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema already documents 'add' and 'remove' with 67% coverage, and the description adds meaningful workflow context by explaining that 'add' expects keys returned from request_image_upload. It also clarifies listing ownership through 'USER'S OWN existing listings'. The un-documented listing_id parameter is partially covered by this ownership framing, but not fully elaborated.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: 'Add and/or remove photos on one of the USER'S OWN existing listings'. It clearly differentiates this from general listing tools by focusing on photos and ownership, and it sets the max image count. It also references the prerequisite request_image_upload tool, making the purpose unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives explicit usage context: 'First call request_image_upload for each new image and upload the bytes, then pass the returned keys in `add`.' It also clarifies that moderation is triggered only for additions. It does not explicitly name an alternative tool for non-image listing updates, but the guidance is otherwise clear.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.